Stem - 1.6 billion - 67.8 by 6 highest contributing countries and the balance of 32.2% by the remaining 153 nations
Statement I : 56% paird by the 4 highest contributing nations (or an average of 14%). Thus amount contributed by the 5th and 6th ranking nation = 67.8 - 56 = 11.8% (or an average of 5.9%). This is all we can deduce...Hence insufficient
Statement II : Country X paid 4.8% of the total expenditure...Insufficient since we do not know how much the others contributed
Statement I and II: Even here we cannot determine whether X was in the Top 6 bracket

For the second question

Statement I : x intercept>1 which means one co-ordinate of the lying on the line k = (x,0) wherein x>0...Now this point can lie within the circle or even outside the circle....hence insufficient

Statement II : Slope of line = -1/10; equation would be y = mx+c ; y=-x/10 + c...This is insufficient too

Statement I and II : one point if (x,0) and the slope is -x/10; however we do not know the y-intercept or the co-ordinates of even a single point on the line...Hence it should be E

For the third question...

Statement I : Over a period of time S: S+B increased...this can happen either because the number of shares in Ruth's portfolio increased or because Ruth disposed off some of her bonds thereby increasing the ratio of shares in the total portfolio...hence insufficient

Statement II: We only know that the total number of S+B increased; this could have happened for 2 reasons; either the number of shares increased or the number of bonds in the portfolio increased; hence insufficient

Statement I and II: S+B increased and S: S+B increased; combining the two we can say that the number of shares in Ruth's portfolio increased